Blu-ray vs HD DVD: The High Definition Format War

DVD has had a good run, but as we move to 1080p HDTVs, the 4.7GB capacity of a standard DVD is becoming a bottleneck. Enter the "blue laser" formats: Blu-ray and HD DVD. They both use a shorter wavelength laser (405nm vs the 650nm of DVD) to pack more data onto the same size disc, but they disagree on almost everything else.

Technical Differences

HD DVD is essentially "DVD++." It uses the same disc structure as DVD, which makes it cheaper to manufacture and easier to ensure backward compatibility. It tops out at 30GB for a dual-layer disc.

Blu-ray, championed by Sony, is more radical. It moves the data layer much closer to the surface of the disc, allowing for a higher numerical aperture and a massive 50GB capacity on a dual-layer disc. The trade-off is that the discs are more fragile and require a special protective coating.

The Codecs

The good news is that both formats have moved beyond MPEG-2. We're now seeing H.264 (AVC) and VC-1 (Microsoft’s codec) being used, which provide much better quality at lower bitrates.

// Comparing capacities:
DVD: 4.7 GB (Single Layer)
HD DVD: 15 GB (Single Layer)
Blu-ray: 25 GB (Single Layer)

Outlook

This is a classic format war. HD DVD has the price advantage right now, but Blu-ray has the capacity and the support of the PlayStation 3. As a developer, the extra 20GB on Blu-ray is tempting for assets, but the manufacturing costs are a concern. I suspect this will come down to which format the big Hollywood studios and the gaming industry get behind. My money is on the one that comes bundled with a game console.